AIM: Prospective survey of the effects of cisapride on QTc interval in neonates given cisapride. METHODS: QTc interval was determined just before and 2.9 (0.9) days after outset of the treatment in 49 neonates treated with cisapride between 1 August 1995 and 29 February 1996. RESULTS: Cisapride significantly increased QTc interval (p = 0.0001), and this was higher when birthweight or gestational age were lower. The prolongation of QTc interval above the arbitrary value of 0.450 (n = 7) was clinically asymptomatic and was significantly more common in the infants born with a gestational age < or = 33 weeks (n = 6). CONCLUSION: The findings indicate that cisapride accumulates in less mature neonates. Further pharmacokinetic studies are needed.